Thyroid and its regulatory hormonal homeostasis in current and the former smokers

Effect of cigarette smoking on serum thyroid hormones,i e.,thyroxine (t4) and tri-iodothyronine (t3) and their regulatory hormone,i.e.,thyrotropin (tsh) was evaluated in male current smokers (n=80),ex-smokers (n=50) and never smokers (n=50),ages ranging 30-60 years. current smokers were categorized as group i (n=40) including short duration (1-5 years) and group ii (n=40) including long duration (6-30 years) smokers. body mass index (bmi),blood pressure (bp) and heart rate (hr) were also recorded. enzyme-linked-immunosorbent assay was used to estimate levels of t4,t3 and tsh. t4 varied non-significantly in comparable groups. t3 and tsh were found to be significantly elevated in current compared to never smokers. elevation in tsh was more intensified in group ii compared to group i. ex-smokers indicated a significant rise in t3 when compared with never smokers. bmi exhibited a significant decline in smokers than never smokers but a highly significant elevation in former compared to current and never smokers. bp decreased significantly in current compared to never smokers. the trend persisted,although less intensified,in former than never smokers. hr,in current and ex-smokers,was significantly elevated as compared to never smokers. the study indicated significant variations in thyroid and their regulatory hormonal pattern in smokers and ex-smokers. bp,bmi and hr also presented significant alterations from the normal pattern. the results,specifically in ex-smokers,have suggested that smoking has long term effects on serum t3. bp and hr. whereas. bmi has shown inverse relationship between current and the former smokers. copyright 2010 zoological society of pakistan.